Resin bound gold nanocomposites assisted SE/ATR-FTIR spectroscopy for detection of pymetrozine insecticide in vegetable samples.

The goal of this work was to assess the competence of organic hydrophobic resin bound gold nanocomposites (OH/R-AuNCs) for detection of pymetrozine insecticide from vegetable samples employing surface-enhanced/attenuated total reflectance-Fourier transform infrared (SE/ATR-FTIR) spectroscopy. The adsorption isotherm models, including the Langmuir, Freundlich and Temkin, are tested to reveal the interactive behaviour between the OH/R-AuNCs and pesticide. The adsorption occurs principally by London-Van der Waals dispersion interactions and hydrogen bonding interactions between the surface of OH/R-AuNCs materials and the hydrophobic part of pesticide molecule. The characteristic absorption band obtained at 3019.94 cm-1 was utilized for the quantitative analysis of pymetrozine insecticide in vegetable samples. The method was found to be accurate and precise, with mean recovery values in the range of 94.5-110 %, correlation coefficient of 0.992 %, and detection limit of 2.65 µg mL-1. The adsorption efficiency of the designed OH/R-AuNCs significantly influences the SE/ATR-FTIR response of the pymetrozine around 90 %. The optimized and validated method was applied to determine the residual concentrations of the pymetrozine that had been applied to vegetable samples.

Sublethal Effects of Spirotetramat, Cyantraniliprole, and Pymetrozine on Aphis gossypii (Hemiptera: Aphididae).

The toxicity and sublethal effects of three insecticides (spirotetramat, cyantraniliprole, and pymetrozine) on Aphis gossypii, a major agricultural pest, were investigated. The nymphal stage showed greater susceptibility than the adult stage to all the insecticides, with a difference of up to 8.9 times at the LC50 of spirotetramat. The effects of sublethal concentrations (LC10, LC30, LC50, and LC70) of the insecticides on the on the developmental period, survival rate, adult longevity, fecundity, and deformity rate were compared with those of the control. Compared with the control, cyantraniliprole and pymetrozine did not significantly affect the developmental period in the parental or F1 generation when applied at the nymphal stage at any concentration. Nonviable nymphs occurred in the F1 generation when both nymphs and adults were treated with spirotetramat and cyantraniliprole but not in the F2 generation. The age-specific maternity (lxmx) of A. gossypii treated with sublethal concentrations (LC10, LC30) decreased with increasing concentration. Spirotetramat at the LC30 resulted in significant differences in all life table parameters (R0, rm, λ, T, DT) compared with those of the control. Similarly, compared with that of the control (43.8), the net reproductive rate (R0) significantly decreased for all the insecticides except cyantraniliprole at the LC10 (37.5). Therefore, this study indicated that sublethal concentrations (over the LC30) of spirotetramat, cyantraniliprole, or pymetrozine might be useful for the density management of A. gossypii.

Method development of multi pesticide residue analysis in country beans collected from Dhaka, Bangladesh, and their dietary risk assessment.

The aim of the study was to develop a modified QuEChERS method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of five multi-class pesticides in country beans collected from Dhaka, Bangladesh. Pesticides were extracted using ACN, and to minimize the co-extraction matrix, optimized d-SPE cleanup was done using sorbents (GCB, PSA, and C18). In the calibration range, the method showed excellent linearity with a correlation coefficient of R2 ≥ 0.9990 both in solvent- and matrix-matched calibration. For the selected pesticides, average recoveries (at four spiking levels (n = 5) of 10, 20, 100, and 200 µg/kg) of 70-100 % were achieved with relative standard deviations (RSDs) ≤ 9.5 %. The limit of detection (LOD) and limit of quantification (LOQ) ranged from 0.3333 to 1.3333 µg/kg and 1.0 to 4.0 µg/kg, respectively. The dietary risk assessment, in terms of hazard quotient (HQ), was calculated to assess consumers' health risks.

Sublethal concentrations of pymetrozine reduce Sogatella furcifera transmission of Southern rice black-streaked dwarf virus.

BACKGROUND: The transmission of plant viruses is closely associated with the specific probing behaviors of the vectors. Pymetrozine is a pyridine azomethine insecticide that interferes with nervous regulation of feeding behavior of piercing-sucking insects. This study aimed to evaluate the potential of sublethal concentrations of pymetrozine in reducing the transmission of Southern rice black-streaked dwarf virus (SRBSDV) by the planthopper Sogatella furcifera. RESULTS: Laboratory assays showed that both acquisition and inoculation rates of SRBSDV decreased significantly in the planthoppers feeding on plants treated with lethal concentrations 10% and 50% (LC10 and LC50 ) pymetrozine compared with the insects feeding on the control plants, for which significant effects of pymetrozine concentration and time post-treatment were detected. Honeydew excretion of the planthoppers showed significant reduction with increasing concentration of the insecticide but no significant association with time post-treatment. Electrical penetration graph recordings revealed that total durations of each waveform in both acquisition and inoculation were significantly affected by pymetrozine treatment, with total durations of non-probing (NP), penetration initiation (N1), and extracellular activity (N3) elongated whereas those of salivation (N2) and phloem-related activities (N4-a and N4-b) shortened. Additionally, both acquisition and inoculation rates were significantly lower at 168 h than at 6 h post-treatment. CONCLUSION: The results indicate that sublethal concentrations of pymetrozine reduce SRBSDV transmission, which is associated with reduction in feeding and alteration in probing behaviors characterized by the prolonged non-probing, penetration initiation and extracellular activity and shortened salivation and phloem-related activities. © 2023 Society of Chemical Industry.

Smartphone-integrated paper-based sensing platform for the visualization and quantitative detection of pymetrozine.

Pymetrozine (PYM) is an effective pyridine insecticide for controlling aphids, while its residues pose a serious threat to human health. Herein, a europium complex (Eu-DBPA, DBPA represents deprotonated 2,5-dibromoterephthalic acid ligand) probe was prepared for the detection of PYM via fluorescence quenching. The detection process has the advantages of short response time (2 min), wide linear range (0-4 and 4-45 mg/kg) and low detection limit (2.2 µg/kg). Furthermore, a portable detection platform was designed by integrating Eu-DBPA-based paper strip with smartphone and applied for the visual detection of PYM in real cucumber, tomato, cabbage and apple samples, obtaining satisfactory recovery (99.00 %-107.00 %) and low standard deviation (RSD < 3.4 %). In addition, a logic gate device was designed to simplify the detection process. The smartphone-integrated paper-based probe detection platform provides a new strategy for intelligent and online identification of hazards in environmental and biological samples.

Residue Analysis and Dietary Risk Assessment of Pymetrozine in Potato (Solanum tuberosum L.) and Chrysanthemum morifolium (Ramat).

Pymetrozine is used on potato (S. tuberosum) and Chrysanthemum morifolium (C. morifolium) to obtain greater yield and quality. However, pesticide use carries the potential for residues to remain and be detected on harvested crops. Therefore, the aim of this study was to estimate pesticide residues in S. tuberosum and C. morifolium products that are commercially available for human consumption and to assess the associated dietary risks. For this study, a total of 340 samples (200 S. tuberosum samples and 140 C. morifolium samples) were collected randomly from supermarkets and farmer's markets. Residues of pymetrozine in S. tuberosum and C. morifolium were detected by using an established and validated QuECHERS-HPLC-MS / MS method, while a dietary risk assessment of pymetrozine in S. tuberosum and C. morifolium was performed using these data. The detection rates of pymetrozine in S. tuberosum and C. morifolium samples were 92.31% and 98.17%, respectively, with residues not more than 0.036 and 0.024 mg/kg, respectively. Based on these results, the dietary risk assessment indicated that the intake of pymetrozine residues in S. tuberosum and C. morifolium does not pose a health risk. This work improved our understanding of the potential exposure risk of pymetrozine in S. tuberosum and C. morifolium.

Reverse genetic study reveals the molecular targets of chordotonal organ TRPV channel modulators.

Insecticides have been widely used for the control of insect pests that have a significant impact on agriculture and human health. A better understanding of insecticide targets is needed for effective insecticide design and resistance management. Pymetrozine, afidopyropen and flonicamid are reported to target on proteins that located on insect chordotonal organs, resulting in the disruption of insect coordination and the inhibition of feeding. In this study, we systematically examined the susceptibility of six Drosophila melanogaster mutants (five transient receptor potential channels and one mechanoreceptor) to three commercially used insecticides, in order to identify the receptor subunits critical to the insect's response to insecticides. Our results showed that iav1, nan36aand wtrw1 mutants exhibited significantly reduced susceptibility to pymetrozine and afidopyropen, but not to flonicamid. The number of eggs produced by the three mutant females were significantly less than that of the w1118 strain. Meanwhile, the longevity of all male mutants and females of nan36a and wtrw1 mutants was significantly shorter than that of the w1118 strain as the control. However, we observed no gravitaxis defects in wtrw1 mutants and the anti-gravitaxis of wtrw1 mutants was abolished by pymetrozine. Behavioral assays using thermogenetic tools further confirmed the bioassay results and supported the idea that Nan as a TRPV subfamily member located in Drosophila chordotonal neurons, acting as a target of pymetrozine, which interferes with Drosophila and causes motor deficits with gravitaxis defects. Taken together, this study elucidates the interactions of pymetrozine and afidopyropen with TRPV channels, Nan and Iav, and TRPA channel, Wtrw. Our research provides another evidence that pymetrozine and afidopyropen might target on nan, iav and wtrw channels and provides insights into the development of sustainable pest management strategies.

Metabolic Resistance of Sogatella furcifera (Hemiptera: Delphacidae) toward Pymetrozine Involves the Overexpression of CYP6FJ3.

Sogatella furcifera (Horváth), which mainly threatens rice, shows various levels of pesticide resistance due to long-term overuse of pesticides. Our resistance monitoring of 20 field populations in Sichuan, China, revealed that they were susceptible to highly resistant toward pymetrozine (0.4-142.2 RR), and JL21 reached the highest level of resistance. The JL21 population exhibited cross-resistance to triflumezopyrim and dinotefuran but sensitivity to sulfoxaflor, acetamiprid, clothianidin, and nitenpyram. The increased P450 activity were support to involve in pymetrozine resistance by detoxification enzyme activities and synergist determination. Among 16 candidate P450 genes, CYP6FJ3 (5.25-fold) was the most up-regulated in JL21, while no significant change was found after LC25 pymetrozine treatment. Furthermore, the knockdown by RNAi and heterologous overexpression by the GAL4/UAS system confirmed that the CYP6FJ3 overexpression was involved in the pymetrozine resistance, and recombination in vitro confirmed that CYP6FJ3 could hydroxylate pymetrozine. Therefore, the overexpression of CYP6FJ3 promotes pymetrozine metabolic resistance in S. furcifera.

Fitness costs of resistance to insecticide pymetrozine combined with antimicrobial zhongshengmycin in Nilaparvata lugens (Stål).

The brown planthopper, Nilaparvata lugens (Stål), is a major pest of rice crops, and its control is critical for food security. Pymetrozine has been recommended as an alternative to imidacloprid for controlling N. lugens, but the pest has developed high resistance to it, making its prohibition and restriction urgent. To address this issue, we conducted a study using a mixture of pymetrozine and zhongshengmycin with the effective ratio of 1:40, to evaluate the fitness costs in N. lugens. Our results showed that N. lugens had a relative fitness of 0.03 under this ratio, with significantly reduced longevity, female and male adult periods, total pre-oviposition days, and fecundity. Moreover, the expression levels of the uricase gene (EC1.7.3.3) and farnesyl diphosphate farnesyl transferase gene (EC2.5.1.21) were reduced in N. lugens. These genes are involved in urea metabolism and steroid biosynthesis pathway, respectively, and their suppression can interfere with the normal nutritional function of N. lugens. Our study demonstrates that the combination of chemical insecticides and antimicrobials can delay the development of resistance and improve the efficiency of pest control. This information is valuable for researchers developing management strategies to delay the development of pymetrozine resistance in N. lugens.

Uptake and Biotransformation of Spirotetramat and Pymetrozine in Lettuce (Lactuca sativa L. var. ramosa Hort.).

Here, we investigated the uptake, transport, and subcellular distribution of the pesticides pymetrozine and spirotetramat, and spirotetramat metabolites B-enol, B-glu, B-mono, and B-keto, under hydroponic conditions. Spirotetramat and pymetrozine exhibited high bioconcentrations in lettuce roots, with both having root concentration factor (RCF) values >1 after exposure for 24 h. The translocation of pymetrozine from roots to shoots was higher than that of spirotetramat. Pymetrozine is absorbed in roots mainly via the symplastic pathway and is primarily stored in the soluble fraction of lettuce root and shoot cells. The cell wall and soluble fractions were the major enrichment sites of spirotetramat and its metabolites in root cells. Spirotetramat and B-enol were mainly enriched in the soluble fractions of lettuce shoot cells, whereas B-keto and B-glu accumulated in cell walls and organelles, respectively. Both symplastic and apoplastic pathways were involved in spirotetramat absorption. Pymetrozine and spirotetramat uptake by lettuce roots was passive, with no aquaporin-mediated dissimilation or diffusion. The findings of this study enhance our understanding of the transfer of pymetrozine, spirotetramat, and spirotetramat metabolites from the environment to lettuce, and their subsequent bioaccumulation. This study describes a novel approach for the efficient management of lettuce pest control using spirotetramat and pymetrozine. At the same time, it is of great significance to evaluate the food safety and environmental risks of spirotetramat and its metabolites.